Radio equipment

ABSTRACT

A radio equipment, wherein an attenuator ( 10 ) is inserted between antennas ( 91, 92 ) and a radio module ( 2 ), and output and input sensitivities are raised and lowered simultaneously so as to keep the balance of a radio covering range with an input receiver coverage at a constant, and the antenna ( 91 ) and the antenna ( 92 ) with attenuator are switched over by a switch ( 8 ) to increase and decrease the radio coverage range and input receiver coverage while keeping the balance of the dynamic radio coverage range with the input receiver coverage.

TECHNICAL FIELD

The present invention relates to a radio equipment for performing radiocommunication, especially control and shaping of a communication range.

BACKGROUND ART

FIG. 12 is a diagram showing a conventional radio equipment. In thediagram, the reference numeral 1 designates a host controller; 2, aradio module; 3, a base band controller; 4, an endless interface; 5, apower amplifier; 6, a low-noise input amplifier; 7, a switch; and 9, anantenna as an inverted F antenna.

In the diagram, the host controller 1 transfers data to the base bandcontroller 3. The base band controller 3 modulates the transferred data.The modulated electric signal is amplified by the output amplifier 5 andradiated as a radio wave from the antenna 9 to space through the switch7. On the other hand, a radio wave propagated through the space isreceived in the antenna 9 and amplified by the low-noise input amplifier6 through the switch 7. Then, the amplified electric signal isdemodulated to data by the base band controller 3 and transferred to thehost controller 1.

In the conventional radio equipment, because the output of the poweramplifier 5 and the input sensitivity of the low-noise input amplifier 6are fixed, the radio coverage range and the input receiver coverage inthe radio equipment are also fixed. Accordingly, when, for example, auser of one radio equipment in which both coverage range and inputreceiver coverage are 10 m wants to communicate with another radioequipment having equal performance, the user (or the radio equipmentitself) can judge whether the other radio equipment is in an area with a10 m radius centering about the user or not.

The user of the radio equipment cannot judge whether any other radioequipment is near the user in the area with a 10 m radius. In otherwords, the user cannot specify who is the other radio equipment existingnear the radio equipment of the user himself/herself. Furthermore, theuser of the radio equipment cannot confirm whether the other radioequipment is coming near to or going far away from the userhimself/herself.

On the other hand, there is a radio equipment in which the output of thepower amplifier 5 is variable. In the radio equipment, however, theratio of output to input sensitivity varies, so that the radio coveragerange depending on the output is not equal to the input receivercoverage of the radio wave depending on the input sensitivity.

When, for example, the output of a radio equipment used as a basestation at a certain point of time is raised, electric field intensityaround the base station becomes so high that the coverage range iswidened. Accordingly, a radio wave from the base station is audible toany radio equipment existing within the widened coverage range. When thebase station calls any ambient radio equipment in this state, theambient radio equipment tries to reply to the base station but linkageto the base station cannot be established because the output of theambient radio equipment is low yet. Furthermore, there is a disadvantagethat normal communication is disabled because the ambient radioequipment does nothing but repeat replying.

When the output of a radio equipment used as a mobile station at acertain point of time is lowered, electric field intensity around themobile station is reduced so that the radio coverage range is narrowed.Accordingly, a radio wave cannot reach any radio equipments around themobile station except radio equipments close to the mobile station. Whena radio equipment not close to the mobile station calls in this state,the mobile station tries to reply to the calling radio equipment becausethe input receiver coverage of the mobile station is kept as it is. Theoutput of the mobile station is however low, so that the radio wavecannot reach the calling radio equipment. Communication with calling theradio equipment is ceased and new linkage cannot be established.Furthermore, there is a disadvantage that normal communication isdisabled because the mobile station does nothing but repeat replying.

In addition, in an environment in which a plurality of mobile stationsgenerate a queue for a radio equipment which is a base station, forexample, in a vending machine (base station) providing service on thebasis of requests from radio equipments (mobile stations), the forefrontof the queue, that is, the first radio equipment as a party to beserviced cannot be identified and priority cannot be distinguishedbetween radio equipments registered as the queue.

DISCLOSURE OF THE INVENTION

An object of the invention is to change both input receiver coverage andcoverage range of a radio equipment dynamically without change of theratio between the two ranges to thereby specify a communication partyand to particularly specify whether the other radio equipment is comingnear to or going far away from the radio equipment.

To achieve the foregoing object, in accordance with the invention, in aradio equipment, a device for changing the intensity of input/outputsignals, specifically, an attenuator is inserted between an antenna anda radio module, and there is provided means for relationally raising andlowering output and input sensitivity by controlling the attenuator.

According to a preferred embodiment of the invention, the distancerelation between radio equipments, especially a sequence of radioequipments registered in a queue and the radio equipment in theforefront of the queue are specified on the basis of difference betweensome radio equipment with which the radio equipment can communicate inan area with a 1 m radius and some radio equipment with which the radioequipment can communicate in an area with a 2 m radius when the radiusas a set value of the attenuator is changed to 2 m and 1 m.

In another embodiment of the invention, in the radio equipment, anantenna and an antenna with attenuator are changed over by a switch sothat the radio coverage range and the input receiver coverage can beincreased and decreased while the balance of the radio coverage rangeand the input receiver coverage is kept good.

In a further embodiment of the invention, linkage of the radio equipmentto any other radio equipment is established, for example, in an areawith a 10 m radius and then the antennas are changed over so thatcommunication is continued while the radio coverage range and the inputreceiver coverage in the radio equipment are enlarged and reducedalternately between the area with a 10 m radius and the area with a 1 mradius. As a result, the radio equipment judges whether the other radioequipment is coming near to or going far away from the area with a 1 mradius.

In a further embodiment of the invention, after linkage to some radioequipment which belongs to a plurality of other radio equipments andwhich is, for example, in an area with a 10 m radius is established, theother radio equipment reaching the area with a 1 m radius is specifiedin such a manner that communication is continued while the radiocoverage range and the input receiver coverage in the radio equipmentare enlarged and reduced alternately between the area with a 10 m radiusand the area with a 1 m radius.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a radio equipment to which the invention isapplied;

FIG. 2 is a diagram showing a radio coverage range in the radioequipment to which the invention is applied;

FIG. 3 is a diagram showing an input receiver coverage of the radio wavein the radio equipment according to the invention;

FIG. 4 is a diagram showing establishment of linkage of the radioequipment according to the invention;

FIG. 5 is a diagram showing changing over the radio coverage range andthe input receiver coverage in the radio equipment according to theinvention;

FIG. 6 is a diagram showing changing over the radio coverage range andthe input receiver coverage and the outline of communication due to atimer;

FIG. 7 is a diagram showing changing over the radio coverage range andthe input receiver coverage and the outline of communication on thebasis of detection means;

FIG. 8 is a graph showing the relation between output and inputsensitivity of the radio equipment according to the invention;

FIG. 9 is a diagram showing a first modified example of the radioequipment to which the invention is applied;

FIG. 10 is a diagram showing a second modified example of the radioequipment to which the invention is applied;

FIG. 11 is a diagram showing a third modified example of the radioequipment to which the invention is applied;

FIG. 12 is a diagram showing a conventional technique;

FIG. 13 is a diagram showing a fourth modified example of the radioequipment to which the invention is applied;

FIG. 14 is a diagram showing a method for mounting the invention in atray of a seat; and

FIG. 15 is a diagram showing a fifth modified example of the radioequipment to which the invention is applied.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a diagram showing an embodiment of a radio equipment to whichthe invention is applied.

In FIG. 1, the reference numeral 1 designates a host controller; 2, aradio module; 3, a base band controller; 4, an radio interface; 5, apower amplifier; 6, a low-noise input amplifier; 7 and 8, switches; 91and 92, inverted F antennas; and 10, an attenuator.

The host controller 1 transfers data to the base band controller 3. Thetransferred data is modulated by the base band controller 3 andamplified by the output amplifier 5, so that the data reaches the switch8 in the outside of the radio module 2 through the switch 7. The antenna91 is connected to the switch 8 whereas the antenna 92 is connected tothe switch 8 through the attenuator 10. When the data reaching theswitch 8 is to be output through antenna, the base band controller 3controls the switch 8 to select either of the antennas 91 and 92. Aradio wave is radiated to space from the antenna selected by the switch8.

Incidentally, the antennas 91 and 92 may be replaced by only one antenna92 and configuration may be made so that the switch 8 can select whetherthe attenuator 10 is to be driven or not. In this configuration, thesame effect as that of the invention can be generated in spite ofreduction in the number of antennas.

On the other hand, a radio wave propagated through space is received ineach of the antennas 91 and 92. The received radio waves (data) areinput from the antenna 91 to the switch 8 and from the antenna 92 to theswitch 8 through the attenuator 10, respectively. The base bandcontroller 3 controls the switch 8 to select either of the data input tothe switch 8. The selected data is input to the radio module 2. The datainput to the radio module 2 is amplified by the low-noise inputamplifier 6 and demodulated by the base band controller 3. Thedemodulated data is transferred to the host controller 1.

FIG. 2 is a diagram showing a radio coverage range in the radioequipment in FIG. 1. The reference numeral 11 a designates a radiocoverage range at an output of 0 dBm; and 11 b, a radio coverage rangeat an output of −20 dBm. In this embodiment, respective outputs of theantennas are set so that electric field intensity at a position in thecoverage range 11 a in the case of output through the antenna 91 becomesequal to that at a position in the coverage range 11 b in the case ofoutput through the antenna 92.

FIG. 3 is a diagram showing an input receiver coverage of the radio wavein the radio equipment in FIG. 1. The reference numeral 12 a designatesan input receiver coverage at an input sensitivity of −72 dBm; and 12 b,an input receiver coverage at an input sensitivity of −52 dBm. In thisembodiment, the switch 8 is changed over so that a radio wave outputfrom a sender in the input receiver coverage 11 a can be received whenthe data received in the antenna 91 is used whereas a radio wave outputfrom the sender of the same output in the input receiver coverage 11 bcan be received when the data received in the antenna 92 is used.

FIG. 4 is a diagram showing establishment of linkage of the radioequipment to which the invention is applied. In the diagram, thereference numeral 13 designates a radio equipment to which the inventionis applied; 14 a and 14 b, conventional radio equipments; 15 a, a radiocoverage range and an input receiver coverage in the radio equipment 13;and 16, a radio coverage range and an input receiver coverage in theradio equipment 14 a.

The radio equipment 13 transmits and receives a radio wave at 10 dBmoutput and −72 dBm input sensitivity without interposition of theattenuator 10 by changing over the switch 8. On this occasion, the radiocoverage range and the input receiver coverage in the radio equipment13, that is, the radius of 15 a is 10 m.

The radio equipment 14 a transmits and receives a radio wave at 10 dBmoutput and −72 dBm input sensitivity. The radio coverage range and theinput receiver coverage in the radio equipment 14 a, that is, the radiusof 16 is 10 m which is equal to that in the radio equipment 13.

In FIG. 4, the radio equipment 13 is within the radio coverage range 16of the radio equipment 14 a whereas the radio equipment 14 a is withinthe radio coverage range 15 a of the radio equipment 13. That is,electric field intensity at the position of each radio equipment is atthe level allowing the output of the other radio equipment to bereceived. Accordingly, each radio equipment is at the distance allowingthe other radio equipment to be called, so that linkage can beestablished.

FIG. 5 is a diagram showing the case where the radio coverage range andthe input receiver coverage of the radio equipment 13 in FIG. 4 ischanged over. In the diagram, the reference numeral 15 b designates aradio coverage range and an input receiver coverage in the radioequipment 13 in the case where a radio wave is transmitted and receivedin the antenna 92 through the attenuator 10. In this case, the radius of15 b is 1 m.

FIG. 5 also shows a state in which the radio equipment 14 a havingestablished linkage to the radio equipment 13 in FIG. 4 is coming nearto the radio equipment 13. In this case, the radio equipment 14 a canonly receive the radio wave output from the radio equipment 13 when theradio equipment 14 a enters the circle of the radio coverage range andthe input receiver coverage of the radio equipment 13 represented by 15b.

Although the output of the radio equipment 14 a is always high, theoutput sensitivity of the radio equipment 13 is lowered by −20 dBm bythe attenuator 10. That is, the input receiver coverage is narrowed to15 b. Accordingly, the radio equipment 13 can only receive the radiowave output from the radio equipment 14 a when the radio equipment 14 aenters the circle of 15 b. That is, when the radio coverage range andthe input receiver coverage of the radio equipment 13 are reduced whilethe ratio between the two ranges is kept constant, the radio equipment13 can communicate with only the radio equipment 14 a which is comingnear to the radio equipment 13.

Assume further that the radio equipment 14 b is in the rear of the radioequipment 14 a sequentially. In this case, the radio equipment 13detects the presence of the radio equipment 14 a and the radio equipment14 b by using the radio coverage range and the input receiver coverage15 a. When the radio equipment 13 changes over the antennas to select 15b as the radio coverage range and the input receiver coverage after thepresence of these radio equipments is detected, the radio equipment withwhich the radio equipment 13 can communicate is only 14 a which iscoming near to the radio equipment 13. In this case, the radio equipment13 can specify an array of radio equipments in the sequence of the radioequipment 14 a and the radio equipment 14 b viewed from the radioequipment 13 by confirming the difference between radio equipments withwhich the radio equipment 13 can communicate, that is, by confirming thepresence/absence of radio equipments before and after change in theradio coverage range and the input receiver coverage. In addition, itcan be specified that the radio equipment 14 a is a radio equipment nearthe radio equipment 13.

As described above in FIGS. 4 and 5, because the radio equipment 13 hasmeans for changing over the radio coverage range and the input receivercoverage, the radio equipment 13 can specify whether the radio equipment14 a having linkage established in the radio coverage range and theinput receiver coverage 15 b is coming near to or going far away fromthe radio equipment 13 after the linkage is established.

When there are a plurality of radio equipments, the radio equipment 13can specify the respective positions of the plurality of radioequipments. In this case, the radio equipments the positions of whichcan be specified may be conventional radio equipments each having aradio coverage range and an input receiver coverage of a predeterminedvalue or about 10 m.

FIG. 6 is a diagram showing communication timing in the case where theradio equipment (radio equipment 13) according to the invention changesover the radio coverage range and the input receiver coverage by atimer. In the diagram, the reference numerals 1301, 1302, 1303, 1304,1305 and 1306 designate calls from the radio equipment 13; 14 c and 14d, conventional radio equipments; and 1401, 1402, 1403, 1404 and 1405,replies from the radio equipments 14 c and 14 d. In FIG. 6, the verticalaxis of the graph shows relative distances from the radio equipment 13to the radio equipments 14 c and 14 d.

The radio equipment 13 outputs a call 1301 with power of 0 dBm at timeT0. Upon reception of the call 1301, the radio equipment 14 c gives areply 1401 at time T1. Continuously, the radio equipment 13 outputs acall 1302 at time T2. Upon reception of the call 1302, the radioequipment 14 c gives a reply 1402 at time T3.

Upon reception of the reply 1402, the radio equipment 13 changes overthe output of the equipment to −20 dBm at the right time on the basis ofthe passage of a predetermined time according to the built-in timer. InFIG. 6, the radio equipment 13 changes over the output so thatchanging-over of the output will be completed at time T5. The radioequipment 13 outputs a call 1303 at time T6. In the diagram, there ishowever no reply from the radio equipment 14 c to the radio equipment 13because the radio equipment 14 c is out of the radio coverage range ofthe radio equipment 13. When there is no reply, the radio equipment 13makes a decision at time T7 that the radio equipment 14 c is notapproaching or is absent in the area with a 1 m radius centering aboutthe radio equipment 13.

Continuously, the radio equipment 13 outputs a call 1304 again at timeT8. At the time T8, the radio equipment 14 c in the area with a 1 mradius centering about the radio equipment 13 can receive the call 1304.Upon reception of the call 1403, the radio equipment 14 c gives a reply1403 at time T9.

Upon reception of the reply 1403, the radio equipment 13 recognizes thepresence of the radio equipment 14 c in the area with a 1 m radiuscentering about the radio equipment 13 and prepares for serviceprovision. The radio equipment 13 returns the output to 0 dBm whilepreparing for service.

The radio equipment 13 outputs a call 1305 with power of 0 dBm at timeT12. Upon reception of the call 1305, the radio equipment 14 d gives areply 1404 at time T13. When the preparation for service is completed inthe meantime, the radio equipment 13 changes over its own output to −20dBm at time T14 and outputs a call 1306. The call 1306 is received inthe radio equipment 14 c waiting for the start of service provision in aneighbor of the radio equipment 13. Upon reception of the call 1306, theradio equipment 14 c gives a reply 1405 at time T15. By such exchange,service is provided to 14 c.

The radio equipment 13 having succeeded in calling the radio equipment14 d at the output of 0 dBm changes over its own output to −20 dBm afterthe passage of a predetermined time according to the timer in the samemanner as described above and detects approach of the called radioequipment 14 d. The radio equipment 13 having succeeded in detecting theapproach begins to prepare for provision of service in the same manneras in the case of the radio equipment 14 c. At the same time, the radioequipment 13 changes over its output to 0 dBm and calls another radioequipment until preparation for provision of service is completed. Whenpreparation for provision of service is completed, the radio equipment13 changes over its output to −20 dBm again. The radio equipment 13 thencalls the radio equipment 14 d kept waiting near the radio equipment 13and begins to provide service. In this manner, the timer is used forefficiently detecting approach of the radio equipment and provingservice.

FIG. 7 is a diagram showing timing of changing over the radio coveragerange and the input receiver coverage and timing of communication in thecase where the radio equipment 13 has a radiation sensor as detectionmeans for detecting other radio equipments. In the diagram, thereference numerals 1307, 1308, 1309, 1310, 1311 and 1312 designatecalls; 14 e and 14 f, radio equipments; and 1406, 1407, 1408, 1409 and1410, replies. The vertical axis shows relative distances of the radioequipment 13 to the radio equipments 14 e and 14 f.

The radio equipment 13 outputs a call 1307 at time T0 and outputs a call1308 with power of 0 dBm at time T2. Upon reception of the call 1307,the radio equipment 14 e gives a reply 1406 at time T1. Upon receptionof the call 1308, the radio equipment 14 f gives a reply 1407 at timeT3.

After confirming the radio equipment replying in the input receivercoverage with a 10 m radius, the radio equipment 13 changes over itsoutput to −20 dBm. In the diagram, changing-over of the output iscompleted at time T4. The radio equipment 13 detects approach of theother radio equipment by a radiation sensor included in the hostcontroller 1. Upon detection of approach of the radio equipment 14 e bythe radiation sensor, the radio equipment 13 outputs a call 1309 at timeT6. In the diagram, the radio equipment 14 e gives no reply to the radioequipment 13 because the assumption that the call 1309 is not for theradio equipment 14 e is made. When there is no reply, the radioequipment 13 recognizes that the called radio equipment is not comingnear to the radio equipment 13. Continuously, the radio equipment 13outputs a call 1310 addressed to the radio equipment 14 e at time T8.Upon reception of the call 1310, the radio equipment 14 e gives a reply1408 at time T9.

Upon reception of the reply 1408, the radio equipment 13 recognizes thepresence of the radio equipment 14 e in the neighbor of the area with a1 m radius centering about the radio equipment 13, so that the radioequipment 13 can confirm the radio equipment reaching a neighbor of theradio equipment 13.

The radio equipment 13 outputs a call 1311 at time T10 and begins toprovide service to the radio equipment 14 e, such as sending of anelectronic ticket, sending of electronic money, provision ofinformation, and so on. When the radio equipment 14 e gives a reply 1409at time T11, the provision of this service is completed.

Until the provision of service to the radio equipment 14 e is completed,the radio equipment 13 does not detect approach of other radioequipments than the radio equipment 14 e. Therefore, upon completion ofthe provision of service to the radio equipment 14 e, the radioequipment 13 returns its output to 0 dBm in order to provide service toanother radio equipment. In the diagram, changing-over of the output iscompleted at time T12.

The radio equipment 13 outputs a call 1312 at time T14 to tell the otherradio equipment that provision of service to the other radio equipmentis enabled. Upon reception of the call 1312, the radio equipment 14 fgives a reply 1410 at time T15. The call 1312 is a call for urging theradio equipment 14 f to come near to the radio equipment 13.

The radio equipment 13 having succeeded in calling the radio equipment14 f at an output of 0 dBm begins to prepare for provision of service.During this time, the radio equipment 13 continuously calls anotherradio equipment newly entering the input receiver coverage of the radioequipment 13. When the radiation sensor detects approach of anotherradio equipment to the neighbor of the radio equipment 13, the radioequipment 13 changes over its output to −20 dBm and specifies the calledradio equipment. The radio equipment 13 having succeeded in specifyingthe radio equipment provides the prepared service. Upon detection ofapproach of another radio equipment at the time of provision of service,the radio equipment 13 specifies the radio equipment continuously at anoutput of −20 dBm after the provision of service and provides service.

When approach of another radio equipment is not detected at the time ofprovision of service, the radio equipment 13 changes over its outputmode to 0 dBm again, calls another radio equipment and urges the radioequipment to come near to the radio equipment 13 if necessary.Accordingly, the radio equipment 13 can control approach of a pluralityof radio equipments and can provide service to the plurality of radioequipments sequentially.

FIG. 8 is a graph showing the relation between output and inputsensitivity in the radio equipment 13. In the graph, the referencenumeral 130 designates input sensitivity of the radio equipment 13; and140 and 141, input sensitivities of a conventional radio equipment.

Generally, the input sensitivity of the radio equipment is set inconsideration of the noise level in the periphery of the radioequipment. Specifically, a noise margin of 50 dB is taken for a requiredsensitivity. That is, the input sensitivity of the radio equipment isdefined in such a manner that a noise margin of 50 dB is added toelectric field intensity in the periphery. The input sensitivity of theconventional radio equipment is −72 dBm.

In the graph, the output of the radio equipment 14 a located at adistance of 0 m is received at the input sensitivity 140 tinged with thenoise margin of 50 dB by the conventional radio equipment located at adistance of 10 m. That is, the outputs of conventional radio equipmentscan be received by each other if the conventional radio equipments areat a distance of 10 m from each other.

Next, communication between the conventional radio equipment and theradio equipment 13 will be described. When the output of theconventional radio equipment is to be received by the radio equipment13, the distance in which the radio equipment 13 with input sensitivityof −52 dBm can keep the noise margin of 50 dB as against the output ofthe radio equipment 14 a located at a distance of 0 m in the graph, thatis, the distance in which the radio equipment 13 can receive the outputof the radio equipment 14 a is 1 m as represented by the position ofinput sensitivity 130 of the radio equipment 13.

On the other hand, when the output of the radio equipment 13 is to bereceived by the conventional radio equipment, the output of the radioequipment 13 located at a distance of 0 m in the graph has been alreadyattenuated by 20 dBm by the attenuator. Accordingly, the distance inwhich the conventional radio equipment with input sensitivity of −72 dBmcan keep the noise margin of 50 dB, that is, the distance in which theconventional radio equipment can receive the output of the radioequipment 13 is 1 m as represented by the position of input sensitivity141 of the conventional radio equipment.

As described above, the radio equipment to which the invention isapplied is not only compatible with the conventional radio equipment interms of connection to the conventional radio equipment at the outputthrough the antenna 91 but also kept compatible with the conventionalradio equipment in terms of connection to the conventional radioequipment even at a near distance of 1 m if the antenna 91 is changedover to the antenna 92 with the attenuator 10.

When the antenna 91 and the antenna 92 are dynamically changed over bythe switch, the radio coverage range and the input receiver coverage canbe dynamically changed over, for example, to 10 m and 1 m.

FIG. 9 is a diagram showing a first modified example of the radioequipment to which the invention is applied. In the diagram, thereference numeral 10 b designates an attenuator; 101, a splitter; and102, a balun or terminator. Data output from the radio module 2 is inputto the attenuator 10 b. Whenever the data input to the attenuator 10 bis split into two by the splitter 101 included in the attenuator 10 b,the intensity of the data is attenuated to a half. The split data isoutput from one branch of the splitter 101 to the antenna 9. The datareaching the other branches are terminated by the terminators 102attached to ends of the branches respectively.

In this modified example, both output and input can be attenuated at thesame ratio by the splitter 101. Accordingly, the radio coverage rangeand the input receiver coverage can be reduced while balance of the tworanges is kept constant.

FIG. 10 is a diagram showing a second modified example of the radioequipment to which the invention is applied. In the diagram, thereference numeral 10 c designates an attenuating device including metalpieces. In the second modified example, the antenna 9 is wrapped in theattenuating device 10 c so that the radio coverage range and the inputreceiver coverage of the radio equipment can be reduced while balance ofthe two ranges is kept constant.

FIG. 11 is a diagram showing a third modified example of the radioequipment to which the invention is applied. In the diagram, thereference numeral 5 a designates a variable output power amplifier; and17, a mixer circuit. The mixer circuit 17 has a noise source 170.

The final stage of the variable output power amplifier 5 a has aplurality of power amplifiers. Accordingly, the output of the variableoutput power amplifier 5 a varies in accordance with the number of poweramplifiers switched on. The plurality of power amplifiers may be allequal in transistor size and area or may be different from one anotherin transistor size and area. Incidentally, the output of the variableoutput power amplifier 5 a increases in proportion to the area oftransistors of power amplifiers switched on. Accordingly, it isnecessary to incorporate the plurality of power amplifiers in thevariable output power amplifier 5 a so that a required output can beobtained in the variable output power amplifier 5 a. The base bandcontroller 3 controls the number of power amplifiers switched on in thevariable output power amplifier 5 a. When, for example, all theplurality of power amplifiers are switched on, a coverage range with a10 m radius is achieved by the variable output power amplifier 5 a.When, for example, only one power amplifier is switched on, a coveragerange with a 1 m radius is achieved by the variable output poweramplifier 5 a.

Data received in the antenna 9 is input to the mixer circuit 17. Themixer circuit 17 mixes the input data with noise generated in the noisesource 170 and outputs the mixture to the low-noise input amplifier 6.Because noise is mixed, the input sensitivity of the low-noise inputamplifier 6 is reduced from −70 dBm to −50 dBm. The base band controller3 suppresses the output of noise by directly controlling the noisesource 170.

According to this modified example, the radio coverage range and theinput receiver coverage can be reduced while balance of the two rangesis kept constant by the radio interface 4 having the variable outputpower amplifier 5 a and the mixer circuit 17. Furthermore, the base bandcontroller 3 can control the radio coverage range by controlling thevariable output power amplifier 5 a. In addition, the base bandcontroller 3 can adjust the input receiver coverage finely bycontrolling the noise source 170.

FIG. 13 is a diagram showing a fourth modified example of the radioequipment to which the invention is applied. In the diagram, thereference numeral 18 designates a printed circuit board; 181, a platemetal conductor which is a ground layer in inner layers of the printedcircuit board 18; 182, a plate metal conductor which is an electricpower supply layer in inner layers of the printed circuit board 18; and93 and 94, antennas.

In the diagram, the radio module 2, the switch 8 and the antennas 93 and94 are mounted on a surface of the printed circuit board 18.

The plate metal conductor 181 as a ground layer and the plate metalconductor 182 as an electric power supply layer are disposed as innerlayers of the printed circuit board 18 successively viewed from the sidenear the radio module 2. The plate metal conductors 181 and 182 supplyelectric power to the radio module 2 and the switch 8.

The antenna 93 is disposed so as to overlap the plate metal conductors181 and 182 viewed from above the printed circuit board 18. When viewedfrom above the printed circuit board 18, the antenna 93 has no portionnot overlapping the plate metal conductors 181 and 182.

The gap between the antenna 93 and nearer one of the plate metalconductors 181 and 182 to the antenna 93 is in a range of from 0.1 mm to2 mm. This gap comes from the thickness of an electrically insulatingfilm inserted between the metal conductors. Sufficient insulationwithstand voltage and parasitic capacitance can be achieved by thisthickness. In this modified example, the printed circuit board 18 isproduced in such a manner that electrically insulating films and metalconductors are piled up alternately like a sandwich. The thickness ofthe printed circuit board 18 is limited to about 2 mm by aboard-producing apparatus. If the gap is secured, sufficient insulationwithstand voltage and parasitic capacitance, however, can be achievedeven in the case where the printed circuit board 18 is about 2 mm thick.Even in a so-called build-up board formed in such a manner that metalconductors and insulators are laminated on an electrically insulatingfilm as a substrate, the same performance as described above can beachieved if the aforementioned gap is selected to be in a range of from0.1 mm to 2 mm.

On the other hand, the antenna 94 is disposed so as not to overlap theplate metal conductors 181 and 182 viewed from above the printed circuitboard 18. When viewed from above the printed circuit board 18, theantenna 94 has no portion overlapping the plate metal conductors 181 and182.

Data output from the radio module 2 is input to the antenna 93 or 94through the switch 8. The switch 8 changes over a circuit so as to beelectrically connected to either the antenna 93 or the antenna 94.

Capacitance is parasitic between the antenna 93 and the plate metalconductors 181 and 182, so that the resonance frequency of the antenna93 is reduced. Accordingly, SWR becomes high, so that the rate ofradiation of electric power from the antenna 93 to space is reduced.

Further, a large part of magnetic flux component of radio wave radiatedfrom the antenna 93 is absorbed to the plate metal conductors 181 and182. Accordingly, when radio wave is radiated from the antenna 93,electric field intensity in a neighbor of the radio equipment becomesweak compared with the case where radio wave is radiated from theantenna 94.

That is, electric power radiated from the antenna 93 to space is lowerthan electric power radiated from the antenna 94 to space because ofgeneration of parasitic capacitance and absorption of magnetic flux. Theantenna gain at the time of input to the antenna 93 is lower than thatat the time of input to the antenna 94.

Accordingly, in this modified example, when the antenna 93 and theantenna 94 are changed over by the switch 8, the radio coverage rangeand the input receiver coverage can be dynamically changed over, forexample, to 10 m and 1 m.

FIG. 14 is a diagram showing a state in which the radio equipment towhich the invention is applied is mounted in a back rest of a seat in anelectric car, an airplane, or the like. In the diagram, the referencenumeral 20 designates a rear surface of the back rest; 201, a traymounted in the rear surface of the back rest; 202, a latch for fixingthe tray; 203, a beam and hinge of the tray; 94 t, a tray built-inantenna on the tray upper surface side; and 94 b, a tray built-inantenna on the tray floor surface side. This diagram shows a state inwhich the tray 201 is fixed to the rear surface 20 of the back rest of afront seat by the latch 202.

The tray 201 includes the radio module 2, the switch 8, the antenna 93,the tray upper surface side tray built-in antenna 94 t, and the trayfloor surface side tray built-in antenna 94 b.

The tray upper surface side tray built-in antenna 94 t and the trayfloor surface side tray built-in antenna 94 b are attenuatingfunction-including antennas. The tray upper surface side tray built-inantenna 94 t has a radiation pattern covering a neighbor of the uppersurface of the tray. The tray floor surface side tray built-in antenna94 b has a radiation pattern covering a neighbor of the floor surfaceside of the tray. The antenna 93 has a radiation pattern widely coveringboth the upper surface side and the floor surface side of the tray.

The radio module 2 uses the antenna 93 when it starts. Then, the radiomodule 2 changes over the used antenna to the tray floor surface sidetray built-in antenna 94 b or the tray upper surface side tray built-inantenna 94 t by using the switch 8 when the radio module 2 begins toprovide service to the user. When the antenna is changed over to theseantennas, the radio equipment built in the tray can communicate with aneighbor of the tray, specifically only a neighbor of a seated personusing the tray. As a result, only the radio equipment used by the userin the seat can communicate with the radio equipment built in the tray.

The radio module 2 detects the position of the tray 201 by detecting thefact that the latch 202 is located in a latch position or the fact thatthe beam and hinge 203 of the tray 201 is not located in a bendingposition. The radio module 2 selects and uses the tray floor surfaceside tray built-in antenna 94 b at the time of storage of the tray 210and the tray upper surface side tray built-in antenna 94 t at the timeof extraction of the tray 201 on the basis of the detected information.

FIG. 15 is a diagram showing a fifth modified example of the radioequipment to which the invention is applied. In the diagram, thereference numeral 183 designates a plate metal conductor in inner layersof the printed circuit board 18; 19, a switch; and 95, an antenna.Incidentally, the switch 19 may be replaced by a relay circuit.

The radio module 2 and the antenna 95 are mounted on a front surface ofthe printed circuit board 18. The switch 19 is mounted on a rear surfaceof the printed circuit board 18.

The plate metal conductor 181 and the plate metal conductor 182 aredisposed as inner layers of the printed circuit board successivelyviewed from the side near the radio module 2. The plate metal conductors181 and 182 supply electric power to the radio module 2 and the switch19.

The antenna 95 is disposed so as to overlap the plate metal conductor183 viewed from above the printed circuit board 18. When viewed fromabove the printed circuit board 18, the antenna 94 has no portion notoverlapping the plate metal conductor 183.

The gap between the antenna 93 and the plate metal conductor 183 is in arange of from 0.1 mm to 2 mm.

Data output from the radio module 2 is input to the antenna 95. Theswitch 19 controls electrical connection between the plate metalconductor 181 as a ground layer and the plate metal conductor 183 byturning on and off.

When the plate metal conductor 181 as a ground layer is electricallyconnected to the plate metal conductor 183 by the switch 19, capacitanceis parasitic between the antenna 95 and the plate metal conductor 183.Accordingly, the resonance frequency of the antenna 95 is reduced, sothat SWR becomes high. Accordingly, the rate of radiation of electricpower from the antenna 95 to space is reduced.

Further, in this case, a large part of magnetic flux component of radiowave radiated from the antenna 95 is absorbed to the plate metalconductor 183. Accordingly, electric field intensity in a neighbor ofthe radio equipment is reduced by about 50 dB in a 2.4 GHz band, thatis, weakened to about 1/250 compared with the case where there is noelectrical connection to the plate metal conductor 183.

Accordingly, when the switch 19 electrically connects the plate metalconductor 181 as a ground layer to the plate metal conductor 183,electric power radiated from the antenna 95 to space is reduced and theantenna gain at the time of input is reduced because of parasiticcapacitance and absorption of magnetic flux.

Conversely, when the plate metal conductor 181 as a ground layer isdisconnected from the plate metal conductor 183 by the switch 19, theeffect of parasitic capacitance and absorption of magnetic flux does notoccur. Accordingly, electric power radiated from the antenna 95 to spaceis unchanged.

That is, in this modified example, when the switch 19 is turned on andoff, the radio coverage range and the input receiver coverage of theradio equipment can be dynamically changed over, for example, to 10 mand 1 m.

Although this modified example has been described on the assumption thatan MOS transistor switch or an electromagnetic relay is used as theswitch 19, a switching regulator having its operation switched on andoff from the outside may be used as the switch 19.

The radio equipment to which the invention is applied can roughlyclassify other radio equipments in a radio network into radio equipmentsout of the input receiver coverage and radio equipments within the inputreceiver coverage by controlling and reducing the input receivercoverage of the equipment itself. The radio equipment to which theinvention is applied behaves as a hidden terminal to the radioequipments out of the input receiver coverage. Because the radioequipment behaves as a hidden terminal, the radio equipment does notreply to the radio equipments out of the input receiver coverage at alland there is no call reaching the radio equipments out of the inputreceiver coverage. In this manner, the radio equipment to which theinvention is applied can divide the radio network dynamically forconvenience' sake.

Furthermore, when the input receiver coverage is reduced, linkagebetween some radio equipment changed from within the input receivercoverage to out of the input receiver coverage and the radio equipmentto which the invention is applied is ceased. Accordingly, the radioequipment to which the invention is applied can be used for constructinga radio network so that linkages between the radio equipment and aplurality of radio equipments can be ceased at once intentionally.

INDUSTRIAL APPLICABILITY

As described above, the invention is useful in dynamically changing theradio coverage range and the input receiver coverage in the radioequipment. The invention is also useful in confirming relative distancesbetween radio equipments. The invention is further useful in exchangingservice efficiently in a radio network.

1. A radio equipment comprising: a host controller; a radio moduleconnected to said host controller; a first antenna; a second antenna towhich an attenuator is connected; and a switch connected to said hostcontroller so as to change over said first antenna and said secondantenna; wherein said host controller controls said switch to selecteither said first antenna or said second antenna, so that when saidsecond antenna is selected, the intensity of a signal input from saidsecond antenna to said radio module and the intensity of a signal outputfrom said radio module to said second antenna are relationallycontrolled, and wherein said host controller controls said attenuator tocontrol input receiver coverage of said second antenna to be narrowerthan input receiver coverage of said first antenna, and wherein whensaid radio equipment transitions from a communication-disabled state toa communication-enabled state, the antenna with attenuator is changed toretrieve the quantity of attenuation of said attenuator forbidding saidradio equipment from receiving a radio wave transmitted from a farspecific radio equipment out of ambient radio equipments and set saidattenuator to the retrieved quantity of attenuation to thereby make saidradio equipment transition to a state forbidding said radio equipmentfrom receiving the radio wave transmitted from said far specific radioequipment.
 2. A radio system including a far specific radio equipment,said for specific radio equipment comprising the radio equipmentaccording to claim 1, characterized in that when a radio wavetransmitted from a radio equipment transitioning to a state forbidding aradio wave transmitted from said far specific radio equipment isreceived by said far specific radio equipment, said far specific radioequipment retrieves the quantity of attenuation of said attenuatorforbidding said far specific radio equipment from receiving a radio wavetransmitted from said radio equipment and sets its own attenuator to theretrieved quantity of attenuation to thereby make said far specificradio equipment transition to a state forbidding said far specific radioequipment from receiving the radio wave transmitted from said radioequipment.
 3. A radio equipment according to claim 1, characterized inthat said radio equipment transitioning to a state forbidding said radioequipment from receiving a radio wave transmitted from a far specificradio equipment reduces the quantity of attenuation of said attenuatorand transmits a radio wave when the quantity of attenuation reaches themaximum value of the attenuating device or exceeds a reference value setin advance or when a predetermined time has passed after the quantity ofattenuation of said attenuator is set.
 4. A radio equipment according toclaim 3, wherein a radio wave transmitted from a radio equipment isinformation (beacon) concerning said radio equipment.
 5. A radioequipment according to claim 1, characterized in that said attenuatingdevice comprises a plurality of final output amplifier portions and thatsaid radio equipment transitioning to a state forbidding said radioequipment from receiving a radio wave transmitted from a far specificradio equipment increases the number of operated output amplifierportions in the plurality of final output amplifier portions to increaseits output when the quantity of attenuation reaches the maximum value ofthe attenuating device or exceeds a reference value set in advance orwhen a predetermined time has passed after the quantity of attenuationof said attenuator is set.
 6. A radio equipment according to claim 5,wherein a radio wave transmitted from a radio equipment is information(beacon) concerning said radio equipment.
 7. A radio equipment accordingto claim 1, wherein a radio wave transmitted from a specific radioequipment is base station information (beacon).
 8. A radio equipmentaccording to claim 1, characterized in that said radio equipmenttransitioning to a state forbidding said radio equipment from receivinga radio wave transmitted from a far specific radio equipment reduces thequantity of attenuation of said attenuator when there is no reply froman ambient radio equipment being in communication with said radioequipment or when error occurs frequently, and keeps the quantity ofattenuation of said attenuator to the reduced value until said radioequipment cuts off communication on the basis of a cut-off requestissued from said ambient radio equipment or on the basis of its owndecision.
 9. A radio equipment according to claim 1, characterized inthat said radio equipment transitioning to a state forbidding said radioequipment from receiving a radio wave transmitted from a far specificradio equipment reduces the quantity of attenuation until some ambientradio equipment is found if there is no ambient radio equipment found,and returns the quantity of attenuation to its original value even at anoutput with the quantity of attenuation of zero.
 10. A radio equipmentaccording to claim 1, characterized in that said radio equipment hasattenuating means for attenuating input/output of radio wave to a levelforbidding said radio equipment from receiving a beacon transmitted froman ambient base station using a common channel when said radio equipmentis in operation.
 11. A radio equipment according to claim 10,characterized in that said attenuating means included in said radioequipment for attenuating input/output of radio wave is added to anantenna so as to be dynamically variable.
 12. An attenuating meansincluded in a radio equipment according to claim 10 for attenuatinginput/output of radio wave, characterized in that gain setting in anoutput stage in which an output is dynamically variable is interlockedwith gain setting in an input stage in which an input is dynamicallyvariable.
 13. A radio equipment according to claim 10, characterized inthat said radio equipment reduces the quantity of attenuation andtransmits a beacon occasionally to thereby notify said ambient basestation using said common channel of the radio equipment's being inoperation.
 14. A radio network comprising: a radio equipment including:a host controller, a radio module connected to said host controller, afirst antenna, a second antenna to which an attenuator is connected, anda switch connected to said host controller so as to change over saidfirst antenna and said second antenna, wherein said host controllercontrols said switch to select either said first antenna or said secondantenna, so that when said second antenna is selected, the intensity ofa signal input from said second antenna to said radio module and theintensity of a signal output from said radio module to said secondantenna are relationally controlled, and wherein said host controllercontrols said attenuator to control input receiver coverage of saidsecond antenna to be narrower than input receiver coverage of said firstantenna; and a group of other radio equipment; wherein said radioequipment uses said switch to change over use of said first antenna anduse of said second antenna so that said radio equipment behaves as ahidden terminal to any radio equipment that belongs to said group ofother radio equipments and that is located at a predetermined distancefrom said radio equipment; and wherein when said radio equipmenttransitions from a communication-disabled state to acommunication-enabled state, the antenna with attenuator is changed toretrieve the quantity of attenuation of said attenuator forbidding saidradio equipment from receiving a radio wave transmitted from a farspecific radio equipment out of ambient radio equipments and set saidattenuator to the retrieved quantity of attenuation to thereby make saidradio equipment transition to a state forbidding said radio equipmentfrom receiving the radio wave transmitted from said far specific radioequipment.
 15. A radio network according to claim 14, characterized inthat said radio equipment transitioning to a state forbidding said radioequipment from receiving a radio wave transmitted from a far specificradio equipment reduces the quantity of attenuation of said attenuatorand transmits a radio wave when the quantity of attenuation reaches themaximum value of the attenuating device or exceeds a reference value setin advance or when a predetermined time has passed after the quantity ofattenuation of said attenuator is set.
 16. A radio network according toclaim 14, characterized in that said attenuating device comprises aplurality of final output amplifier portions and that said radioequipment transitioning to a state forbidding said radio equipment fromreceiving a radio wave transmitted from a far specific radio equipmentincreases the number of operated output amplifier portions in theplurality of final output amplifier portions to increase its output whenthe quantity of attenuation reaches the maximum value of the attenuatingdevice or exceeds a reference value set in advance or when apredetermined time has passed after the quantity of attenuation of saidattenuator is set.
 17. A radio network according to claim 14,characterized in that said radio equipment transitioning to a stateforbidding said radio equipment from receiving a radio wave transmittedfrom a far specific radio equipment reduces the quantity of attenuationof said attenuator when there is no reply from an ambient radio being incommunication with said radio equipment or when error occurs frequently,and keeps the quantity of attenuation said attenuator to the reducedvalue until said equipment cuts off communication on the basis of acut-off request issued from said ambient radio equipment or on the basisof its own decision.
 18. A radio network according to claim 14,characterized in that said radio equipment transitioning to a stateforbidding said radio equipment from receiving a radio wave transmittedfrom a far specific radio equipment reduces the quantity of attenuationuntil some ambient radio equipment is found if there is no ambient radioequipment found, and returns the quantity of attenuation to its originalvalue even at an output with the quantity of attenuation zero.
 19. Aradio equipment comprising: a host controller; a radio module connectedto said host controller; a first antenna; a second antenna to which anattenuating device is connected; and a switch connected to said hostcontroller so as to change over said first antenna and said secondantenna; wherein said host controller controls said switch to selecteither said first antenna or said second antenna, so that when saidsecond antenna is selected, the intensity of a signal input from saidsecond antenna to said module and the intensity of a signal output fromsaid radio module to said second antenna are relationally controlled,and wherein said host controller controls said attenuating device tocontrol input receiver coverage of said second antenna to be narrowerthan input receiver coverage of said first antenna, and wherein saidhost controller switches, during time of communicating with anotherradio equipment through said first antenna, from said first antenna tosaid second antenna after a predetermined time according to timer todetermine whether said radio equipment is in said state of receiving noreply transmitted from said other radio equipment thereby to determine adistance between said radio equipment and said other radio equipment.20. A radio equipment comprising: a host controller; a radio moduleconnected to said host controller; a first antenna; a second antenna towhich an attenuating device is connected; and a switch connected to saidhost controller so as to change over said first antenna and said secondantenna; wherein; said host controller controls said switch to therebyselected either said first antenna or said second antenna, so that whensaid second antenna is selected, the intensity of a signal input fromsaid second antenna to said radio module and the intensity of a signaloutput from said radio module to said second antenna are relationallycontrolled, said host controller controls said attenuating device tocontrol input receiver coverage of second antenna to be narrower thaninput receiver coverage of said first antenna, said host controllercontinues to select said antenna to continue to communicate with otherradio equipment when said radio equipment is in a stat receiving replytransmitted from said equipment is in a state receiving replytransmitted from said another radio equipment, and said host controllerdetermines whether said radio equipment is in said state of receiving noreply transmitted from said far specific radio equipment when said radioequipment is not in a state receiving reply transmitted from said farspecific radio equipment.
 21. A radio equipment comprising: a hostcontroller; a radio module connected to said host controller; a firstantenna; a second antenna to which an attenuating device is connected;and a switch connected to said host controller so as to change over saidfirst antenna and said second antenna; wherein: said host controllercontrols said switch to there select either said first antenna or saidsecond antenna, so that when second antenna is selected, the intensityof a signal input from said second antenna to said radio module and theintensity of a signal output from said radio module to said secondantenna are relationally controlled, said host controller controls saidattenuating device to control input receiver coverage of said secondantenna to be narrow than input receiver coverage of said first antenna,said host controller continues to select said second antenna to continueto communicate with other radio equipment when said radio equipment isin a state receiving reply transmitted from said equipment is in a statereceiving reply transmitted from said another radio equipment, and saidhost controller continues to select said first antenna until preparationof service is completed when said radio equipment is in a state ofreceiving reply transmitted through said antenna from said far specificradio equipment, and switches to said second antenna when saidpreparation service is completed.